Fittings of this type are used, for example, in the construction of aircraft, in which not only the fulfillment of stricter safety requirements is of the utmost importance, but also an effective weight reduction.
When installing cables in aircraft, the required cable lengths can sometimes be significantly reduced by installing such cable leadthroughs. However, the cable leadthrough mostly is also subject to strict requirements.
In addition to the installation of various cables in the vicinity the frame, the utilization of cable leadthroughs frequently makes it possible to realize new installation routes, which may require a modification of the cable mounting. A cable leadthrough frequently needs to fulfill the function of a mounting element for cables to be installed.
The requirements to be fulfilled by a cable leadthrough can be elucidated particularly well on the example of supply lines for appliances in on-board kitchens. Several on-board kitchens are typically arranged in central regions of the aircraft fuselage. Since kitchen supply cables have a comparatively large conductor cross section due to high supply currents, it is common practice to realize such kitchen supply cables in the form of a bunched adapter cable. Such adapter cables connect individual distribution panels to one another. One preferred location for accommodating central distribution panels is the region of the cross members in the interior of the fuselage. The on-board kitchens are equipped with a separate distribution panel. Such a distribution panel was usually arranged in the ceiling of the on-board kitchen until now in order to install all supply lines leading from the distribution panel to the individual kitchen appliances through the kitchen ceiling. This provides the advantage that the needed cable leadthroughs in the ceiling area are not affected by possibly spilled liquids in the kitchen area and that such liquids cannot reach the installation areas. Consequently, the risk of liquid-related short circuits can be maintained low. However, one significantly disadvantage of this installation principle can be seen in the long installation routes that sometimes need to be bridged between the central distribution panel and the kitchen distribution panel with heavy adapter cables. For example, if a central distribution panel is situated in the cross member region, above which a kitchen cell is arranged, the adapter cable needs to be installed from the central distribution panel to the outer wall of the fuselage, then, to a location above the ceiling of the kitchen, between the frames along the outer wall and then to the distribution panel above the ceiling of the kitchen cell. In case that the adapter cable has a weight between approximately 160 g and more than 300 g per meter, the required cable lengths have a significant weight. In case that the kitchen distribution panel would be arranged in the lower region of the kitchen cell, the utilization of a suitable cable leadthrough in the floor of the on-board kitchen would make it possible to significantly reduce the length of the adapter cables between the distribution panels and to simultaneously reduce the weight accordingly.
However, the design of the cable leadthrough needs to fulfill certain requirements in order to allow its utilization at such a sensitive location.
It should be possible to install the cable leadthrough in a relatively simple fashion, in particular it is of the utmost importance that individual cable components do not become damaged under any circumstances because the possible fire hazard associated with such damages represents a safety risk of the first order on board of aircraft. In addition, it must be securely prevented that liquids leaking through the opening in the floor of the kitchen that is used for installing the cable leadthrough. This aspect is also very important because on the one hand the handling of meals and beverages in the kitchen area increases the risk of spilling liquids, for example, as a result of turbulences. On the other hand, safety-relevant installations that are sensitive to liquids may be arranged directly underneath the on-board kitchen in the region of the cross members. It is absolutely imperative to protect such installations from being unintentionally affected by liquids. It also needs to be taken into account that the properties of the cable leadthrough may not vary, namely even under extreme accelerations for components of this type. For example, an effective strain relief needs to occasionally absorb forces in the region of the cable leadthrough that can amount to a multiple of the loads generated by the weight of the cable. Possibly separating objects should not be able to cause any changes in the seating of the installed cable. Abrupt loads during intense turbulences and possibly required emergency landings also may not affect the electrical installations because the full functionality of all important operating systems needs to be ensured, particularly in such instances. A cable leadthrough also may not impair the cleaning and maintenance of the aircraft.
There may be a need for a fitting that may realizing a liquid-tight cable leadthrough that only requires a low installation expenditure, may ensure a sufficient strain relief and/or may conform to the high safety standards in aircraft construction.